This invention relates generally to the field of wafer processing and, more particularly, to a system and method for determining a position error in a wafer handling device.
Probers, steppers, wafer inspection systems, integrated circuit mounters, bonders, and other wafer handling devices typically must accurately position wafers of integrated circuits before operating on the wafers. For example, a prober must accurately position a wafer before electrically testing the integrated circuits mounted to the wafer. If the prober correctly positions the wafer, testing probes touch and electrically couple to contact points, allowing the prober to test the integrated circuits. If, however, the prober incorrectly positions the wafer, the testing probes may miss the contact points, and as a result, the prober may be unable to test the integrated circuits. Even worse, the testing probes may accidentally touch and damage integrated circuits on the wafer. To avoid these and other positioning problems, wafer handling devices typically uses high-precision lead screws, air bearing tables, or other mechanical devices to properly position wafers.
Unfortunately, wafer handling devices still suffer from position errors due to manufacturing faults, mechanical wear and stress, temperature variations, and other sources of positioning inaccuracies. Faults in the construction of lead screws, bearings, bushings, or other physical components introduce positioning inaccuracies in wafer handling devices, and mechanical stress and wear further deteriorate the positioning accuracy of these devices. Chucks, tools, and the electronic motor drive provide still another source of position errors. By causing materials to expand or contract, temperature variations also affect the position of a wafer in a wafer handling device. Due to these and other factors, wafer handling devices often improperly position wafers during operation.
In accordance with the present invention, a system and method for determining a position error in a wafer handling device is provided that substantially eliminates or reduces disadvantages or problems associated with previously developed systems and methods.
In one embodiment, a system for determining a position error in a wafer handling device includes a control module, an image acquisition module, and an image analysis module. The control module moves a workpiece having one or more reference marks, and the image acquisition module captures an image of at least one reference mark. The image analysis module, which is coupled to the image acquisition module, compares the captured image to stored target information to determine a position error.
The technical advantages of the present invention include a system and method for determining a position error in a wafer handling device. By using automatic visual inspection technology, the system and method accurately and efficiently identify a position error, determine a direction and magnitude of the position error along one or more axes, and generate control information to correct the position error. When in a calibration mode, the system and method profile the positioning accuracy of a wafer handling device over a specified plane of operation, generate control information to improve the positioning accuracy of the wafer handling device, and store the control information for future use by the wafer handling device. When in a real-time error correction mode, the system and method identify and correct position errors as a wafer handling device operates on a wafer. Other technical advantages are readily apparent from the attached description, figures, and claims.